Motor-controlling system.



PATENTED JUNE 6, 1905.

A. G. EASTWOOD.

MOTOR CONTROLLING SYSTEM.

APPLICATION FILED 00124, 1904.

A RFEET SHEET 1.

No. 791,887. PATENTED JUNE 6, 1905.

A. G. EASTWOOD. MOTOR CONTROLLING SYSTEM.

APPLICATION FILED OUT. 24, 1904.

PATENTED JUNE 6, 1905.

A. G. EASTWOOD. MOTOR CONTROLLING SYSTEM.

APPLICATION FILED 00124, 1904.

4 SHEETS-SHEET 3.

Cicwfw o PATENTED JUNE 6, 1905.

A. O. EASTWOOD.

MOTOR CONTROLLING SYSTEM.

APPLICATION FILED OCT. 24, 1904.

4 SHEETS-SHEET 4,

frwewfiow- (ZPA fiJ/U CFcwZu/wd; W w @6607 a- UNITED STATES PatentedJune 6, 1905.

ARTHUR C. EASTWOOD, OF CLEVELAND, OHIO.

MOTOR-CONTROLLING SYSTEM.

SPECIFICATION forming part of Letters Patent No. 791,887, dated June 6,1905.

Application filed October 24, 1904. Serial No. 229,835.

1'0 (0Z7 whom, 17/; nmy concern:

Be it known that I, ARTHUR (l. EASTWOOD, a citizen of the United States,residing in Cleveland, Ohio, have invented certain Improvements inMotor-Controlling Systems, of which the following is a specification.

One object of my invention is to provide an improved system forcontrolling the operation of series reversing motors or reversing shuntor compound wound motors whose speed is varied by varying the fieldstrength.

A further object of the invention is to provide a system whereby thearmature of a motor, and consequently the mechanism attached thereto,may be reversed as rapidly as is consistent with the current-carryingcapacity of the motor and the mechanical strength of the various movingparts and no more rapidly. I also desire to provide a system includingapparatus which shall limit the flow of current through themotor-windings to a predetermined safe value and also to provide meanswhereby the flow of current shall be maintained equal or up to saidvalue.

\Vhen an electric motor is reversed while its armature is in motion as,for example, by reversing the connections of the armature to the sourceof currentsupplythe counter electromotive force generated by the forwardrotation of the armature is added to the applied voltage, resulting inan effective voltage higher than that of the current-supply, which tendsto force current through the armature. The additional electromotiveforce so produced is maintained until the armature has come to rest, andwhen the latter starts to turn in its reverse direction the counterelectromotive force generated by it is opposed to and therefore issubtractive from the applied voltage.

In the case of a compound-wound motor operating with constant fieldstrength the voltage which would be effective in forcing current throughthe armature and the resistance in series with it will at the instant ofreversal be almost double the line voltage, since the counterelectromotive force in an eflicient motor will be very nearly equal tothe applied voltage. In a patent granted to me on October 11, 190a, No.772, 277, l have described and claimed a system providing an extraamount of resistance, substantially equal to the starting resistance ofthe motor, for limiting the current to its normal starting value whenthe motor is suddenly reversed. In the case of a variable-speed motor,however, the electromotive force generated by the armature at theinstant of reversal of its connections to a supply-line may be very muchhigher than the voltage of said line. For example, considering the caseof a motor operating at three hundred revolutions per minute with fullfield strength, it may be assumed that this will run at twelve hundredrevolutions per minute with a weakened field, as might occur in the caseof a series motor whose full-load speed was three hundred revolutionsper minute, but which was operated at a light load. If the connectionsof the armature were suddenly reversed while the motor was running atfull speed and at the same time the field was brought up to normalstrength, the armature would in a short time generate a counterelectromotive force approximately equal to four times its normal counterelectromotive force. It the motor were operated on atwo-hundred-and-twenty volt circuit and its eiliciency was such that itsnormal counter electromotive force was two hundred and ten volts, thearmature at the instant of reversal would generate eight hundred andforty volts. and this plus the applied voltage of two hundred and twentywould give a voltage of ten hundred and sixty available to force currentthrough the resistance.

If one hundred amperes be assumed as the maximum safe value of thecurrent, a resistance of 10.6 ohms must be provided to limit saidcurrent to this amount at the instant of reversal. To maintain as nearlyas possible a constant flow of one hundred amperes during the period ofreversal, this resistance should be gradually reduced as the armatureslows down until when the armatureis at rest only 2.2 ohms should be incircuit, so as to still allow a flow of one hundred amperes at theapplied voltage of two hundred and twenty. This resistance of 2.2 ohmsshould be then gradually cut out as the armature is accelerated in areverse direction, and my invention is intended to providea systemwhereby the resistance will be cut into and out of circuit with. themotor as above described.

In the accompanying drawings, Figure 1 is a diagrammatic view showing myinvention as applied to and operated in connection with a shunt-woundmotor whose speed is varied by varying its field strength. Fig. 2 is adiagrammatic view showing my invention as applied to the operation of aseries-wound motor. Fig. 3 is a diagrammatic view showing my inventionas applied to the operation of a shunt-wound motor provided with areversing.- controller having four running-points. Fig. 4 showsmyinvention as applied to a compound-wound motor and particularly designedto bring the armature of they motor to rest in aminimum time aftercurrent has been cut off. Fig. 5 is a diagrammatic view showing myinvention as applied to the operation of a series motor controlled byelectromagnetic reversing-switches whose coils are supplied with currentthrough a hand-operated controller, and Fig. 6 is an elevationillustrating one operative form of connection between the blades of twoswitches employed in some forms of my invention.

Referring to Fig. 1 of the above drawings, A is the armature of a motorhaving a shunt field-winding a and which is provided with a bank ofstarting resistance divided in two sections R and R. There is inaddition a bank of braking resistance divided into three sections R Rand R, which is connected in series with one terminal of the main switchM and the starting resistance. In addition there are two rheostats r and1*, each having an adjustable contact-arm r and contact-buttons inconnection with various points of bodies of resistance, as shown,whereby the amount of current flowing to the shunt-field of the motormay be varied.

A reversing-controller is provided for the motor having two series ofcontact-segments C and C and a number of fingers, hereinafter referredto, for engagement with said segments. Respectively connected to theends of the sections R R and R are three switches S, S, and S normallymaintained in their closed positions and provided with operatingcoilsall connected in multiple across the terminals of the armature A. Inaddition there are three switches S S, and S connected to the ends andto the point of junction of the two sections of resistance R and R, thecoil of the'first of these switches being connected at one end to afinger 5 of the reversing-controller, while its other end is connectedwith one end of the coils of switches S and S to a wire in connectionwith one pole of the main switch. The other ends of the coils ofswitches S and S are connected, respectively, to those switch -terminalsin permanent connection with the sections R and R in the manner and forthe purpose set forth in my Patent No. 7 7 2,27 7.

The three switches S, S, and S are so constructed as to normally remainin their open positions, while two additional switches S and S,respectively, connected to short-circuit the rheostats r and 1 areconstructed to normally remain closed, their coils each having one endconnected to a terminal of an auxiliary switch designed to be closed bythe closing of switch S and supplied with current from one pole of themain switch M. The second ends of these coils are respectively connectedto fingers 7 and 6 of. the reversing-controller. Said controller is inaddition provided with fingers 1, 2, 3, and 4, and four segments in eachof the groups C and C are so interconnected as to reverse theconnections of the armature A to the supply-mains in the well-knownmanner.

A yoke-piecey extends between the blades of switches S and S in suchmanner that both of them are necessarily in their open or closedpositions at the same time.

Under operating conditions, with the main switch M closed and thesegments C of the reversing-controller in engagement with theirrespective fingers, current Wlll flow from said switch through the coilof switch S to finger 5 of the reversing-controller, thence through twoof the segments C to finger 4., and so to the negative supply-main. Thisenergization of said coil closes the switch S and permits current toflow to the motor-armature through sections R and R of the resistance.Current simultaneously flows to the field-winding a from the positiveside of the switch S, through both of the normally closed switches S andS and back to the negative terminal of said switch S. The switches S"and S will now successively and automatically close as the motoraccelerates, the closing of the latter switch closing the auxiliaryswitch 8, thereby supplying current to the coil of switch S, currentflowing from finger 6 of the controller to certain of the segments ofthe group 0, through finger 4:, and thence to one of the supply-mains.This energization of the coil of switch S causes it to open, and therebythrows into series with the shunt-field a a certain portion of theresistance of the rheostatr, as determined by the position of itsadjustable arm r. This resistance weakens the current flowing throughthe field, thereby causing the motor to still further speed up.

It will be seen that as soon as currentis supplied to the armature A theswitches S and S immediately open, owing to the energization of theircoils by the counter electromotive force of the armature, while theswitch S tends to open, but cannot, owing to its being yoked to switch Swhich is closed, so that if the reversing-controller be operated tobring its segments '0 into engagement with the fingers said switches Sand S will still be held open and switch S will open,

IIO

since said coils are still excited by said counter electromotive force.Even though the circuit through the coil of switch S be now completed asbefore this switch cannot close by reason of the yoke-bar y, which holdsit open because switch S is open, so that current from the supply-mainsis compelled to flow through the three sections of resistance R R andR", as well as through the two sections of starting resistance R and R,being thereby limited to a safe amount. I have shown this bar 1/ indiagram in Figs. 1 and 2, and while it may take the form of any rigidconnection between the blades of adjacent switches I have shown in Fig.6 one of such forms.

As the armature A slows down and its counter electromotive forceconsequently falls the switches S, S, and S successivelyclose, sincethey are adjusted to overcome the pull of their magnets at successivelylower voltages, the switch S closing first, so as to shortcircuit thesection R, and the switch S linally closing, so as to cut out the lastportion of the braking resistance. Such deenergization of the coil ofswitch S, as well as the fact that the coil of switch S is alreadyenergized from the supply-mains, causes the closing of said switch S",after which the armature will be automatically accelerated, as before,with the exception that since the linger 7 is'cngaged by one of thesegments C, while the linger 6 is open-circuited the switch S will beopened, thereby throwing the resistance of the rheostat 1* into serieswith the shunt-field a. The switches S and S will again be opened andthe coil of switch S energized by the counter electromotive force of themotor-armature, so that when the controller is again operated to reversethe motor the above-described cycle of operations will be repeated.

The two rheostats are employed, as shown, in order that, if desired, themotor may be accelerated to different speeds after successive reversals.

\V hen it is desired to operate a series motor according to myinvention, I have found it desirable to provide what I designate aspilot-coils for each of the switches S, S, and S, so as to insure theirremaining open while the reversing-controller is being operated to moveone set of segments out of engagement with the lingers and to bring theother set of segments into such engagement. Otherwise if said controllerwere operated slowly the counter electromotive force of the motor wouldfall to zero, owing to the dying down of its field. In order to overcomethis objection, I provide auxiliary windings s for each of saidswitches, as illustrated in Fig. 2, connecting all of these windings inseries and bringing their terminals to two fingers 9 and 10 on thereversirig-controller, it being noted that the pilot-winding on switch Sis so proportioned that the energization of the coil of switch S causesboth switches to close, even though said first-named coil be alsoenergized. In order that these pilot-coils may be excited before themain circuit of the motor is closed, I form the segments engaging thelingers 9 and 10 as well as two others of the segments of both groups Cand C so as to engage said lingers before the others, thus insuring theswitches S, S, and S being open and all of the resistance R R", and R incircuit when the connections of the armature to the line are reversed.

It will be seen that the segments coacting with the lingers 9, 10, and11 while engaging said fingers as the controller is operated from itsoff position before the others of the segments are of such a length thatwhen the controller is in itsfull on position with the motor operatingin either direction said three segments are out of engagement with saidfingers. IVith this construction it will be seen that as the segments C,for example, are moved into engagement with their respective fingerscurrent will liow from the positive side of switch M to linger l1,thence to two of the segments (f to linger 10, then to all of the coilss flowing from them to linger 9, through two others of the segments (Jto finger 8, and so to the negative side of switch M. All of theswitches S, S, and S are therefore open, after which the engagement ofthree of the segments 0 with fingers 1, 2, and 3 completes the circuitfrom the switch M through the armature A, series field F, and startingresistance R and R up to the switch S. This is finally closed by theexcitation of its coil from current supplied from the positive side ofswitch M flowing through all of the braking resistance and thence to theupper terminal of said switch, the end of said coil being connected tolinger 12, which is engaged by a relatively short one of the segments Cin connection with the segments engaging linger 8, which, as beforenoted, is connected to the negative side of the switch M. The closing ofswitch S starts the motor, and it will be noted that simultaneously withsuch starting the fingers 9, 10, and 11 pass off of their segments,while switches S, S, and S are still maintained open, since their maincoils are connected, as before noted, in multiple with the armature A.

In Fig. 3 the reversing-controller is made so as to be available foroperating the motor with any number of the resistance-sections R, R, orR continuously in circuit. In this instance the coils of thebraking-switches S, S, and S are connected in series, though, as before,they are excited by the counter electromotive force of the armature. Theadjustment of each of these switches is such that as the motor-armatureslows down and its counter electromotive force gradually falls theswitch S will first close and then the switches l S and S in succession.In this instance there is provided an additional switch S forcontrolling the additional section of resistance B. One terminal of theactuating-coil of switch S is connected to one pole of main switch M,while its second terminal is connected to a finger 13 on thereversing-controller. Similarly one terminal of each of the switches S,S, and S is respectively connected to some point in the startingresistance, as set forth .in my above-mentioned patent, while the secondends of said coils are respectively connected to fingers 14;, 15, and 16on the said controller. The segments for engaging the fingers 13 to 16.inclusive, are of successively-decreasing lengths, so that as thecontroller O is operated the finger 13 is first engaged and afterwardthe fingers 14 to 16 in succession; By this means if the controller beoperated to its extreme position in either direction the motor will beoperated as described in connection with Fig. 1, whereas if saidcontroller be stopped so that fingers 15 and 16 are not engaged by theirrespective segments the motor will be accelerated until the switch Scloses, after which it will continue to run with sections of resistanceR and R in series with its armature.

Fig. 4 shows my improved system as applied to the operation of acompound-wound motor, the shunt-field being indicated at a and theseries field at F. As before, the coils of switches S, S, and S areconnected in series, so as to be energized by the counter electromotiveforce of the armature, though in this instance switch S is designed tonormally remain open. The coils of switches S, S, S, and S while eachhaving one terminal connected, as referred to in my above-mentionedapplication for patent, have their second terminals all connectedtogether and to the negative pole of the main switch M, there being,however, a controlling-switch s interposed between them and said mainswitch. This controlling-switch may be operated automatically by anydesired mechanism, such as the float T, and when closed will permitswitches S S, S, and S to successively close, and so automaticallyaccelerate the motor. After the switch S closes the coils of switches S,S, and S are energized by the counter electromotive force of thearmature A, so that the first two of them open, while the last, thoughtending to close, is prevented from doing so by reason of a locking-bars, which prevents said switches S and S both being in a closed positionat the same time. The opening of the controlling-switch s open-circuitsall of the coils of switches S S, S, and S consequently allowing theseswitches to open, and since the coils of switches S, S, and S are stillexcited by the counter electromotive force of with the sections R R andR of the resistance, and as the speed of the armature is graduallydecreased switches S and S successively close until when the speed ofthe armature, and consequently its counter electromotive force, hasfallen to zero, the switch S opens, and the motor may be started again,as above noted.

In that application of my system shown in Fig. 5 I provide a controllerO, having all of its contacts arranged as segments supported in a singleplane and provided with an operating-handle 0. series type, is providedwith a reversing mechanism' consisting of four switches S, S S and Seach of which is provided with a coil having one end connected to thenegative su pply-main. The second ends of the coils of switches S and -Sare connected to a segment 0 of the controller C, while the second endof the coils of each of the switches S and S is connected to segments 0.A bank of starting resistance, divided in three sections R, R, and-R isconnected to the motor and to the supply-mains through switches S, S, S,and S, as shown in Fig. 3, there being in addition a body of brakingresistance R in shunt to the terminals of switch S The actuating-coilsof switches S, S and S are The motor, which is of the respectivelyconnected to the controller 0 5 through auxiliary switches, each ofwhich is placed to be closed by the switch which under operatingconditions is actuated just before the one having the correspondingcoil. In addition to the above there is acoil 8, con- IOO nected inshunt to the armature-terminals of the motor and active upon an armatureconnected to a movable blade 8 A locking-bar 8 extends between thisblade and the blade of switch S so that as long as coils is suflicientlyenergized said switch cannot close. Locking-bars s and s extend betweenthe blades of switches S and S and S and S respectively, so that but oneswitch of each set can be in a closed position at the same time. Oneterminal of the actuating-coil of switch S is connected to the segments0' of the controller, while segments 0 are connected to one of thesupply-mains through main switch M. One terminal of each of theauxiliary switches 8 s, and s is connected to segments 0 0, and c of thecontroller 0.

With the main switch closed and the operating-handle 0 moved as far asit will go in one direction-as, for example, the position indicated bythe lines a: wswitches S and S of the reversing mechanism will beclosed, as will also switch S Current is thus ap IIS theoperating-handle c be moved into the position y y, the coils of switchesS S and S will be open-circuited, after which the coils of switches S,S, and S will be supplied with current, so that the two former of thesewill immediately close. The latter switch is maintained open, since thecounter electromotive force of the armature of the motor operates theblade as soon as the coil of switch S was open-circuited, therebyholding the locking-bar in such position that the blade of said switchcould not close. Current from the supply-mains must, therefore, flow tothe armature through the braking resistance R, as well as through thestarting resistance R, R, and R. hen the counter electromotive force ofthe armature has fallen to zero, the coil 8 permits motion of the blades so as to allow the switch S to close, and the above-described cycle ofoperations again takes place.

I claim as my invention 1. The combination of a motor having means forconnecting it with current-supply mains and means including a bank ofnormally shortcircuited resistance and controlling switches forautomatically maintaining the flow of current through thearmature of themotor above a predetermined minimum other than zero for a predeterminedtime after said armature has been disconnected from the supply-mains,substantially as described.

2. The combination of a motor, means for reversing the same, and meansfor automatically causing a step-by-step variation of the current-flowoccurring between the time when current is applied after operation ofthe reversing means and the time the armature reverses its direction ofrotation, substantially as described.

3. The combination of a motor, reversing means for the same, a body ofresistance and a series of automatic switches, said switches includingmeans whereby they are caused to successively operate to cutout saidresistance between the time that the reversing means is operated and thetime when the armature reverses its direction of rotation, substantiallyas described.

at. The combination of a motor, two bodies of resistance, automaticswitches for cutting said resistanceinto and out of circuit with themotor, and means for reversing the motor, a plurality of said switcheshaving operating mechanism arranged and connected to cause them to cutout of circuit one of the bodies of resistance after the motorconnections are reversed and before the armature reverses its directionof rotation, substantially as described.

The combination of a motor, two bodies of resistance, two series ofautomatic switches connected to respectively short-circuit sections oftheir respective bodies of resistance, one of said series of switcheshaving its actuating-coils connected to cause its switches to operatesuccessively as the counter electromotive force of the motor rises andthe other series of switches having their actuating-coils connected tocause operation of their switches as the counter electromotive force ofthe motor falls, substantially as described.

6. The combination of a motor, an automatic switch for connecting themotor to supply-mains, a body of resistance connected to be in serieswith said motor and said switch, a second automatic switch forcontrolling the insertion of said resistance in circuit, and means formechanically connecting the blades of said switches so that closing oropening of one efiects the closing or opening of the other,substantially as described.

7. The combination of a motor, an automatic switch for connecting thesame to supply-mains, a bank of resistance, and a second automaticswitch in shunt thereto, said parts being connected to be in series withthe motor, and a bar between said two switches construct-ed to cause theoperation of one of the said switches to effect operation of the other,substantially as described.

8. The combination of a motor having means connecting it withsupply-mains, a body of resistance, and a series of automatic switchesfor cutting said resistance out of circuit, said switches havingactuating-coils connected between, the armature-terminals of the motorand being adjusted to operate successively as the counter electromotiveforce of the motor falls, substantially as described.

9. The combination of a motor having means connecting it tosupply-mains, a body of resistance, and a series of automatic switchesfor cutting said resistance out of circuit, said switches havingactuating-coils connected between the armature-terminals of the motorand being adjusted to operate successively as the counter electromotiveforce of the motor falls, with a reversing device and means forautomatically accelerating the motor after said device and said switcheshave been operated, substantially as described.

10. The combination of a series motor, a body of resistance, a switchfor connecting the motor to current-supply mains, a series of automaticswitches connected to out said resistance into and out of circuit withthe motor, said resistance being in shunt to said first switch, each ofsaid switches having two actuatingcoils, one of which is connectedacross the armature-terminals of the motor and the other is providedwith means whereby it may be connected to the supply-mains,substantially as described.

11. The combination of a series motor, a body of resistance, a switch inshunt thereto for connecting the motor to the current-supply mains, aseries of automatic switches connected to out said resistance into andout of circuit with the motor, each of said automatic switches havingtwo actuating-coils, of Which one is connected across thearmature-terminals of the motor and the other is provided with meanswhereby it may be connected to the supply-mains, with areversing-controller having means for breaking the connection betweenthe switch-coils and the supply-mains after the motor-armature has begunto generate an electromotive force, substantially as described.

12. The combination of a series motor, a body of resistance, a switch inshunt thereto for connecting the motor to current-supply mains, a seriesof automatic switches connected to cut said resistance into and out ofcircuit with the motor, each of said switches having twoactuating-coils, of which one is connected across the armature-terminalsof the motor and the other is provided with means whereby it may beconnected to supply'mains, with a reversing-controller havingcontact-fingers and segments through which said second coils of theautomatic switches are connected to the supply-mains, said segmentsbeing placed to break the connections between the mains and said coilswhen the controller is in its full on position, substantially asdescribed.

13,. The combination of a motor having means connecting it with currentsupply mains, a body of resistance and a series of automatic switcheshaving means continually tending to maintain them in a closed position,

- the coils of said switches being connected across thearmature-terminals of the motor, substantially as described.

14. The combination of a motor, a body of resistance, a switch in shuntto said resistance for connecting the motor to supply-mainsindependently of the same, a series of automatic switches having meanstending to keep them closed and connected to short-circuit portions ofsaid resistance when in such closed position, and actuating-coils forholding the switches in their open position, said switches beingadjusted to close when ditferent voltages are applied to their coils,substantially as described.

15. The combination of a motor, two bodies of resistance connected withthe motor in series with current-supply mains, two series of switchesfor respectively short-circuiting portions of the respective bodies ofresistance, certain of the switches having means continually acting tomaintain them closed and others having means continually acting to holdthem open, with actuating-coils for the switches placed to act againstsaid means, the coils of certain of said switches being connected acrossthe terminals of the motor-armature, substantially as described.

16. The combination of a motor, a body of resistance, a switch orswitches for controlling the placing of said resistance in circuit withsaid motor, said switch or switches each having a plurality ofactuating-coils with a controller having means for connecting certain ofsaid coils to a source of current, said means being disconnected fromsaid source when the motor has begun to generate an electromotive force,substantially as described.

17. The combination of a motor having means for connecting it withcurrent-supply mains, means for connecting said motor in a circuitindependent of said mains and means including a plurality of switcheshaving independent actuating means for automatically causing astep-by-step variation of the current-flow through said motor after itsarmature has been disconnected from said supplymains, substantially asdescribed.

18. The combination of a motor having means for connecting it withcurrent-supply mains, means for connecting said motor in acircuitindependent of said mains, with means including a plurality ofswitches having independent actuating means for automaticallymaintaining the flow of current through the armature above apredetermined amount above zero, for a predetermined time after it hasbeen disconnected from the supply-mains, substantially as described.

19. A system including an electric motor and apparatus for controllingthe currentflow thereto, said apparatus including a plurality ofautomatic switches having independent actuating means and provided witha bar rigidly connecting their movableelements in such manner that saidswitches are either both open or both closed simultaneously,substantially as described;

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

ARTHUR O. EASTWOOD.

Witnesses:

J. E. WELLMAN, G. W. CoMsTooK.

